X, Y = map(int,input().split())
N = int(input())
A = list(map(int,input().split()))

X /= 3.6
Y /= 3.6
XY_distance = 0
ans = "YES"

for c in range(N-1):
	s = A[c] / X
	XY_distance = (Y - X)*s
	if(round((A[c+1] - A[c]),6) < round(XY_distance,6)):
		ans = "NO"
		break
print(ans)